1. Field of the Invention
This invention relates to fittings for flexible hoses, and in particular concerns reusable fittings that can be detached from a worn hose and re-used with a new hose, in the field by an end-user, without requiring special tools or the application of excessively high torque.
2. Prior Art
The invention is particularly advantageous for end fittings and couplings on flexible hoses of the type used for sanitary conduit, but is also useful in other situations. Sanitary conduit is useful or required by many industries, such as the dairy, beverage, food processing and pharmaceutical industries. One option for sanitary conduit is stainless steel piping. Another option has been flexible hose. In a fixed installation, the useful life of flexible hose is generally much shorter than that of stainless steel piping. It becomes necessary to service and replace worn hoses when in contrast, stainless steel piping may last indefinitely.
On the other hand, flexing requirements or the like may be such that flexible hose is preferred over stainless steel piping for a given use. Flexible hose is easier to configure and reconfigure in a given plumbing situation. Replacement of the flexible hose is not so problematical given that flexible hose is relatively inexpensive. End-fittings and couplings for flexible hose, however, are relatively costly. It is advantageous to enable change-over of fittings from a worn hose to a new hose, i.e., to replace only the worn flexible tubing part of the connections, to save costs. For that purpose, the end-fittings should advantageously permit change-over at the site of the installation, preferably by the end-user and without requiring special tools.
The end fittings generally involve a structure that is complementary to another fitting for connecting the hose in fluid communication with another conduit, and structure that provides a fluid-tight connection between the fitting and the hose. U.S. Pat. No. 5,176,411- DuPont, Jr. discloses an example of a fitting for a flexible hose. The DuPont fitting comprises a body, a collar and a sleeve. The collar has a through-bore, and has a counter-bore extending inward from one end of the collar. The through-bore is slightly tapered or conical. The counter-bore has an internal thread. The sleeve has an outside shape that is likewise tapered or conical to match the collar's internal taper. These parts are arranged inside and outside the hose at the end and are arranged together to grip the hose.
More particularly, the end of the hose is strung through the collar and the sleeve, i.e., the collar and sleeve are pushed down on the outside of the hose from the end, to a position out of the way. Thus the hose is prepared for frictional engagement on the body. The body includes a nipple with threads near its base, external barbs near its head, and a shoulder between the thread and barbs. The hose is frictionally forced onto the nipple until the end abuts against the shoulder with the barbed portion inside the hose. The outer diameter of the nipple preferably is slightly larger than the inner diameter of the hose at rest, such that the hose is slightly stretched or swollen in the process of being forced onto the nipple.
The sleeve is then slid back toward the end of the hose from its out-of-the way position to a position encircling the nipple inside the hose. The collar is likewise retrieved from its out-of-the way position to a position surrounding the sleeve. The collar and nipple threads are then meshed, and tightening the tapered collar on the nipple wedges the tapered sleeve, until the sleeve deforms and tightly grips the outside of the hose. The hose thus is squeezed inside and outside between the sleeve and nipple, sufficiently to obtain a fluid-tight or air-tight seal with the fitting. In the DuPont fitting, the internal barbs grip the inside of the hose to prevent axial dislocation of the hose from the fitting.
U.S. Pat. No. 5,240,291 - Zornow discloses another fitting for flexible hose. The Zornow hose comprises a body and nut only. The nut has a through-bore, and has a counter-bore extending inward from one end to a shoulder. The through-bore has a screw or machine type thread pitched in one direction, and the counter-bore has biting threads pitched in the other direction. The biting threads are coarse and are arranged cylindrically, for biting into the outside of the hose and generally forming complementary threads on the outside of the flexible hose. The nut is twisted onto the flexible hose via the biting threads of the counter-bore until the end of the hose abuts against a shoulder in the nut. At that point, the nut and hose are ready for accepting the body.
The body has a nipple with a screw or machine thread near its base, and a slightly conical but nearly cylindrical portion near its head. The head inserts through the screw thread of the nut until the complementary screw threads of the nipple and nut enmesh. Tightening the body relative the nut pushes the head of nipple farther into the hose in the area of the biting threads of the nut and presses the hose outwardly to grip it tightly between the head of the nipple and the biting threads of the nut. The opposite pitches of the biting threads and the screw or machine threads prevent the hose from turning out of the nut as the nut and body are tightened. Here, the counter-clockwise threads of the nut that bite into the outside of the hose prevent axial displacement of the hose, i.e., the tendency for the hose to pull away from the fitting due to internal pressure or mechanical tension.
Fittings such as those disclosed in Zornow and DuPont are commercially available in a variety of sizes, and commercial stocks are kept for sizes up to four-inch (10 cm) diameter hoses or larger. However, such fittings have the drawback that they require rather substantial torque to force the respective threaded parts together sufficiently to grasp the inside and outside surfaces of the hose. Fully tightening the nuts on the fittings may require numerous turns, and the jamming action employed makes it necessary to apply progressively increasing torque. The initial turns may be accomplished by hand. Intermediate turns require wrenches. The final turns at the limits of jamming together the parts, especially for large hoses and fittings, require such torque as to be accomplished most readily only on a stable support for the fitting, such as a bench vise, to permit sufficient torque to be applied to one part of the fitting while holding another. This state of matters frustrates the goal of designing the fitting for installation in the field by the end-user without the need for benches, vises, special tools and the like, which are not often conveniently available near the place of installation of the hoses.
Substantial torque may also be required to unloosen the nuts from the fittings. It typically takes more torque to initially "break" or "crack" the nut, than it took originally to fully tighten the nut, thus being even more likely to require stable clamping of the fitting in a bench vise or the like. Thus the prior art fittings are not ideally suited for field use by the end-user without special tools, vises, heavy tackle and so on.
Insofar as the prior art fittings cause deformation of fitting parts, such as in DuPont, the fittings may be further rendered difficult to disassemble. Moreover, such deformation is such that new parts are needed for at least certain deformable parts of the fittings when installing fittings on a new hose, e.g., as in DuPont's collar, which once deformed may be difficult or impossible to slide over a new hose.
What is needed is a fitting for flexible hoses that solves these and other problems characteristic of conventional fittings, which is relatively handily attached to and detached from a hose, is relatively inexpensive, and which dependably provides a tight and secure sanitary seal.